### Q.35:- If the diameter of a carbon atom is 0.15 nm, calculate the number of carbon atoms which can be placed side by side in a straight line across length of scale of length 20 cm long.

**Answer:-**Diameter of a carbon atom = 0.15 nm = 0.15×10^{-9} m = 1.5×10^{-10 }m

Length along which atoms are to be placed = 20 cm = 2×10

^{-1 }m∴ No. of C-atoms which can be placed along the line = 2×10

^{-1 }m/1.5×10^{-10 }m = 1.33×10^{9}